The environment of commercial, high-rise and low-rise buildings are often controlled by a variable air volume (VAV) box which regulates the air flow within the building. The VAV system includes a controller with an actuator which opens and closes a damper allowing air to flow into the building. The controller modulates the position of the damper by sending a signal to the actuator. The actuator causes the damper to open and close thereby controlling the amount of air flow. The controller receives a signal based on the ambient temperature measured at the thermostat. The ambient temperature is compared to the pre-set, desired temperature and a signal is generated based on the difference between the desired temperature and the actual, measured temperature. The controller responds to the generated signal. The actuator opens or closes the damper in response to the generated signal.
For example, if the ambient air temperature is less than the desired, pre-set temperature, the actuator will open the damper (in one of the system types) thereby allowing the heated or cooled air will flow into the building. There are a number of different types of VAV systems, some of which have the damper normally closed, or normally open. Some VAV systems use hot water reheat to control the VAV. In all of the systems it is important that the ambient temperature be accurately calibrated.
Pneumatic devices are typically used to measure the thermostat pressure. The “spring range” of the actuator is the amount of pressure required to modulate the opening of the actuation. For example, in a normally closed (damper) system, if the ambient temperature is 70 degrees Fahrenheit, the thermostat pressure is 7 psi and the spring ranges are 8–15 psi, i.e. 8–15 psi is required to open the actutator. In a normally open system, the spring ranges are 0–6 psi.
The pneumatic thermostat calibration devices may include a hollow needle attached to a pneumatic sensor. The sensor detects the pneumatic pressure when its needle is inserted into a pneumatic thermostat receiver.
When the control or desired pressure, and the corresponding temperature, of the pneumatic thermostat requires adjustment, a tool is employed to make the adjustment. One of the major drawbacks to the present thermostat calibration devices is that they typically do not include the thermostat adjustment tool with the pressure measuring device and a separate tool must be employed. Further, the different VAV systems which require different types of tools to adjust the different thermostats.
One of the problems encountered with currently-used thermostat calibration devices, is the needle is often vulnerable to clogging and/or damage. Lint, dust and/or other material may clog the sensor rendering it inoperable. The sharp needle may also pose a safety hazard to the user. The unprotected needle may prick or scratch the user when not in use. The unprotected needle is also subject to breakage.
A pneumatic thermostat calibration device with a removable cover to protect the sensor needle from clogging and/or damage and the user from needle induced injury is needed. The pneumatic thermostat calibration device should also be sized to fit in the pocket of a user. There has been a long-standing need for a pneumatic thermostat calibration device which includes a universal thermostat adjustment tool.